The present invention is related to maskless fabrication techniques and, more particularly, to techniques that rely on optical curing of a polymeric material.
Physics based techniques have created a revolution in the computer chip industry and have been further developed in sophisticated applications using silicon and glass for building traditional integrated circuits (IC) through processes including photolithography, etching techniques, and deposition. These processes often have limitations including fabrication cost, clean-room conditions, labor intensive processes, and material technologies. Thus, alternate technologies have evolved including soft lithography, nanoimprint lithography, microcontact printing, and capillary lithography. One of the common features of many of these techniques is that they utilize a mold of either silicon or polymer, which is brought into contact with an underlying mask containing the essential fabricated features. These systems require access to specific equipment and also significant fabrication time for each component. The original process of hard lithography has been augmented with the advent of soft lithography, which allowed a master mold to be developed and then used to produce many copies with polydimethylsiloxane or other polymers.
One example of a maskless optical fabrication system is disclosed in U.S. Pat. No. 6,841,340 to Tani. Tani discloses a highly accurate structure optically fabricated simply and in a short time. Rough optical fabrication using an ultraviolet-irradiation optical fabrication process is carried out for a photo-curing resin by emission of a laser beam from a first light source, and thereafter, fine optical fabrication using a two-photon absorption optical fabrication process is carried out by emission of a laser beam from a second light source. As a result, it is possible to realize optical fabrication which allows fabrication of a fine structure using a two-photon absorption optical fabrication process while realizing high speed processing using the ultraviolet-irradiation optical fabrication process.
Another example of a maskless optical fabrication system is disclosed in U.S. Pat. No. 6,410,213 to Raguin et al. Disclosed therein is a system for the fabrication of arbitrary profile micro-optical structures (lenses, gratings, etc.) and, if desired, with optomechanical alignment marks simultaneously during fabrication, upon the use of low-contrast photosensitive material that, when exposed to a spatially variable energy dosage of electromagnetic radiation, can be processed to achieve multi-level or continuous surface-relief microstructures. By varying the exposure dose spatially based upon predetermined contrast curves of the photosensitive material, arbitrary one-dimensional (1-D) or two-dimensional (2-D) surface contours, including spherical, aspherical, toroidal, hyperbolic, parabolic, and ellipsoidal, can be achieved with surface sags greater than 15 μm. Surface profiles with advanced phase correction terms (e.g., Zernike polynomials) can be added to increase the alignment tolerance and overall system performance of the fabricated structure can also be fabricated. The continuous-relief pattern can be used as is in the photosensitive material, transferred into the underlying substrate through an etch process, electroformed into a metal, or replicated into a polymer.